In an optical system for a surveillance purpose electronic imaging device, an optical system having extremely wide field of view and high resolving power has been required, for example, Japanese Patent Publication No. 2992547, and Japanese Patent Application Laid-Open Nos. 2002-72085, 2003-232998, 2004-29282, 2005-195624, and 2006-119368. A surveillance purpose lens specifically includes a general image-taking lens (a camera lens), a lens for securing safety of the inside and outside of a building, a lens for gathering image information inside or outside of a movable instrument such as a car, a lens for an eye of a robot, a lens for keeping security of an airplane, and a lens for celestial observation.
Those lenses used for such purposes are required to have a wide angle of view, high resolving power, and little ghost images capable of handling wider luminance difference, so that a wide-angle lens for such purposes has to have small number of air interfaces, simple lens configuration, and well-corrected aberrations.